This invention relates to a wavelength driving divice for monochromators.
There are known two types of wavelength driving devices, that is, a sine bar type and a cam type. FIG. 4 schematically shows a wavelength driving device a of a sine bar type which comprises a shaft b having a threaded portion, a nut d engaging the threaded portion of the shaft so as to be moved axially thereof and a light dispersing element such as a diffraction grating c mounted on a plate f provided with an arm g engaging the nut d so that as the nut is moved, the plate f and the grating c thereon is turned for dispersion of the light incident thereon. In this device, the amount of displacement of the nut d is proportional to the wavelength of the light beam from the monochromator. Therefore, by rotating the shaft b to displace the nut d linearly it is possible to drive the wavelength linearly. However, since the precision or accuracy with which the shaft, the nut and other parts are machined directly influences the precision or accuracy of measurement, after the parts have been assembled, the device must be adjusted for accurate and precise operatin. Moreover, since the feeding shaft has a low efficiency of transmission of the driving force, in order to speed up wavelength driving the motor e must be a large-sized, expensive one capable of producing a large torque.
In the wavelength driving device of the cam type, the cams must be manufactured with a high degree of accuracy and precision with resulting increase in the manufacturing cost.
Accordingly, the primary object of the invention is to provide a wavelength driving device for use in monochromators, which eliminates the above-mentioned difficulties, and is simple in construction, capable of driving wavelength at high speed and yet low in the manufacturing cost.